Measuring AC energy flow direction

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  • NorthGuy
    NorthGuy Solar Expert Posts: 1,913 ✭✭
    Re: Measuring AC energy flow direction
    BB. wrote: »
    From the utility and wiring point of view, they supply current. Say for example, you use 100 amps during 1/2 a cycle and consume 100 amps during the other 1/2 cycle. From the kWH point of view, the power used is Zero kWH. But, from the wiring and utility point of view, there is 100 amps of current flow heating the wire and the generator has to source/sink that current--taking generating/distribution resources "without payment".

    When you have an inductive load, such as motor, especially with bad power factor, you draw current during most of the cycle, but there is a short period when you actually supply current back to the source. This, definitely, should be Ok with them, although it does increase losses in the wires.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Measuring AC energy flow direction
    NorthGuy wrote: »
    When you have an inductive load, such as motor, especially with bad power factor, you draw current during most of the cycle, but there is a short period when you actually supply current back to the source. This, definitely, should be Ok with them, although it does increase losses in the wires.

    And why large commercial customers actually have a PF meter that (in our area, I believe) measure the worst case 15 minute power factor and then use 1/PF to apply to the monthly bill (it actually may be the worst 15 minutes in a 1 year period--so can be very costly)... So, for many customers with motors/inductive loads, it makes a lot of sense to add capacitor banks to their process equipment to keep the PF near 1.0 (typically only correct to 0.95 to prevent other problems with oscillations/self excitation of motors when turned off, etc.).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: Measuring AC energy flow direction
    BB. wrote: »
    F
    So, technically, in the above example, you actually have 1.0 PF because the current is perfectly in phase with the voltage (definition of PF), but, I would argue violates the "no generation" policies of most utilities. And at high power levels can create "flickering" as the voltage differences between the output/loading parts of the cycle.
    -Bill

    I have to take issue with you there Bill. The in-phase/out-of-phase measurement is only part of the Power Factor. It is what is also called phase Power Factor. True Power Factor can be seen as the combination of phase PF and distortion PF. It is the integrated instantaneous power (total wattage) divided by the product of the RMS voltage and the RMS current.

    Leaving reverse power flow out of it completely, a triac driving a resistive load will have a phase power factor of 1, but a distortion PF quite a bit less than 1, giving an overall PF less than 1.
    Same thing for switching power supplies with an input capacitor after a rectifier. The phase PF there is very close to 1, but I have not heard anyone argue that their overall PF is 1.

    In the case of the buy/sell, the current is always *sort of* in phase with the voltage, but it switches direction twice in the middle of each cycle at a point where the voltage does NOT switch direction. If you were selling only, as a pure GTI, the phase calculation would give you a PF of -1 (=cos(180)) rather than 1.
    For the triac-controlled load, adding up exactly equal (in power) periods of +1 and -1 would give you PF=0.
    SMA SB 3000, old BP panels.
  • NorthGuy
    NorthGuy Solar Expert Posts: 1,913 ✭✭
    Re: Measuring AC energy flow direction
    inetdog wrote: »
    For the triac-controlled load, adding up exactly equal (in power) periods of +1 and -1 would give you PF=0.

    I thought the goal was not to transfer power in any direction. PF is a ratio of real power to the apparent power. If real power is zero, PF is zero too.

    Triac, however produces a lot of apparent power because large currents are flowing back and forth. W = 0; VA big; PF = 0

    A range of heaters would do a better job because apparent power would be zero too and it would be no current at all. W = 0; VA = 0; PF = ? (no power - no PF :D) But OP said they were not linear :confused:
  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: Measuring AC energy flow direction
    NorthGuy wrote: »
    I thought the goal was not to transfer power in any direction. PF is a ratio of real power to the apparent power. If real power is zero, PF is zero too.

    Triac, however produces a lot of apparent power because large currents are flowing back and forth. W = 0; VA big; PF = 0

    A range of heaters would do a better job because apparent power would be zero too and it would be no current at all. W = 0; VA = 0; PF = ? (no power - no PF :D) But OP said they were not linear :confused:
    I was referring to equal power in different parts of a single cycle. Should have made that clearer. The question is whether that kind of behavior would raise any flags in the meter.

    I think the OP did not realize that you would turn the various heaters on and off in binary combinations and just looked at the load with a single chosen heater turned on. Very non-linear that way.
    SMA SB 3000, old BP panels.
  • NorthGuy
    NorthGuy Solar Expert Posts: 1,913 ✭✭
    Re: Measuring AC energy flow direction
    inetdog wrote: »
    The question is whether that kind of behavior would raise any flags in the meter.

    May be OP could post the picture of the meter. There are guys around here who know lots about meters. They may be able to figure that out by looking at the picture.
  • lazza
    lazza Solar Expert Posts: 336 ✭✭✭
    Re: Measuring AC energy flow direction

    HI guys

    The meters in question that Endesa are installing are ENEL Cerm1 type. That our friends at Endesa, instead of programming them for net-metering, are kindly programming them to add any excess PV production to your consumption bill... that must breach European or National laws, surely.. but ours is not to reason why, ours is but to pay and cry!

    Attachment not found.

    They can be programmed with a Motorola device, but only Endesa have access to these controllers

    Cheers
    Larry
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Measuring AC energy flow direction

    In the US, it is common for new meters to bill for current flow in either direction... It is not uncommon for people to wire up their meters backwards (put upside down in socket, etc.) to reduce their power usage (growing pot and just saving money). That and other "revenue guard" options such as indicating back to the utility if power is ever cut to the meter.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • lazza
    lazza Solar Expert Posts: 336 ✭✭✭
    Re: Measuring AC energy flow direction

    HI

    I've just found this information on the ENEL electricity meters. It looks like the minimum timespan for sampling positive and negative energy is 1 minute. Therefore I assume a triac type of control wouldnt cause issues on the readings.... is this correct?
  • stephendv
    stephendv Solar Expert Posts: 1,571 ✭✭
    Re: Measuring AC energy flow direction

    This does exactly what you want: http://www.immersun.co.uk/ for about 400 euros. (again apologies if reposting, can't remember whether i posted it here or somewhere else)
  • metalmagpie
    metalmagpie Registered Users Posts: 1
    Re: Measuring AC energy flow direction

    I know its simplistic but I will ask anyway, The point at which the PV panels stop exporting electric and the supplier starts selling to the house is that at which the nett current in the main feed cable is zero. Either side of zero we need to initiate and action.
    Use a current transformer to sample the current, when it is zero switch a load, such as an immersion heater on. If the current falls then we are, or were exporting, if it fell but is still not zero we can increase the energy to the heater until the current is zero. The load in the house is now been met by the PV. If the current increases then we were importing and we reduce the PV load until a minimum or zero is attained. Then we repeat the above.
    It seems to me that the above could be attained by sampling the current at each peak of the AC cycle checking for zero and comparing with the previous value to achieve the action to either increase or decrease the additional load.If the adjustment was the wrong way, ie and increase in load did not achieve a reduction in sensed net current then the next cycle would detect this and reverse the previous action. An Scr could do the switching. I could write this in machine code but that is too old hat I am afraid. Probably ther is a big flaw in this!!!
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Measuring AC energy flow direction

    Same problem: how do you tell if the current in the main line is power coming from the utility or going to it? As current it looks the same.

    It needs to be measured at three points to determine a differentiation which indicates which direction the power transfer is going: GTI output, utility mains feed, load connections.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Measuring AC energy flow direction

    Think of pedaling a tricycle... From standing to the side, you cannot tell if a child is pedaling to make it go faster or "back pedaling" to make it slow down...

    You have to measure the forces and when they are applied to the pedals to figure out the direction (and amount) of power being applied.

    Similar with AC power--You have the Voltage sine wave, but you have to know the Phase, Amplitude, and Direction of current flow at each point in the sine wave to figure out direction and power.

    AC power is actually a very complex set of math--Which is why a genius like Tesla could come up with a better method of distributing power than Edison could (who experimented to learn vs studying the math).

    http://en.wikipedia.org/wiki/War_of_Currents

    It is not "obvious" to figure out the answers to these questions.

    And welcome to the forum "metalmagpie".

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: Measuring AC energy flow direction
    Same problem: how do you tell if the current in the main line is power coming from the utility or going to it? As current it looks the same.

    It needs to be measured at three points to determine a differentiation which indicates which direction the power transfer is going: GTI output, utility mains feed, load connections.
    Actually, measuring only the current or only the voltage does not give you the information you need regardless of how many points you measure it at. (Exception: you can measure the voltage accurately enough at two points to do a shunt calculation to determine the current, but I am not allowing that.)
    You need to know the magnitude and direction of both voltage and current at the same time at the same point to get the exact value of power flow past that point. And you have to know the two at all points in the AC cycle, not just as averages.
    SMA SB 3000, old BP panels.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Measuring AC energy flow direction
    inetdog wrote: »
    Actually, measuring only the current or only the voltage does not give you the information you need regardless of how many points you measure it at. (Exception: you can measure the voltage accurately enough at two points to do a shunt calculation to determine the current, but I am not allowing that.)
    You need to know the magnitude and direction of both voltage and current at the same time at the same point to get the exact value of power flow past that point. And you have to know the two at all points in the AC cycle, not just as averages.

    Voltage in a grid-tie household system is the same at all points, or close enough for practical purposes, as it is set by the Voltage source power supply; the grid. As has been repeatedly hammered into my deteriorating brain capacity the GTI is a current-based power source; its Voltage is fixed by the utility supply.

    As such:
    Loads are always negative power.
    GTI is always positive power (supplying loads and/or grid).
    Grid is either positive power (supplying) or negative power (consuming from GTI).
    Any one can be at zero power.
    If Loads > GTI output then Grid is positive power source.
    If Loads < GTI output then Grid is negative power source.
    If Loads = GTI output then Grid is at zero (exact power balance and highly unlikely).
  • solar_dave
    solar_dave Solar Expert Posts: 2,397 ✭✭✭✭
    Re: Measuring AC energy flow direction
    Voltage in a grid-tie household system is the same at all points, or close enough for practical purposes, as it is set by the Voltage source power supply; the grid. As has been repeatedly hammered into my deteriorating brain capacity the GTI is a current-based power source; its Voltage is fixed by the utility supply.

    As such:
    Loads are always negative power.
    GTI is always positive power (supplying loads and/or grid).
    Grid is either positive power (supplying) or negative power (consuming from GTI).
    Any one can be at zero power.
    If Loads > GTI output then Grid is positive power source.
    If Loads < GTI output then Grid is negative power source.
    If Loads = GTI output then Grid is at zero (exact power balance and highly unlikely).

    That is exactly how the TED does net metering measurement. Read GTI and subtract the loads reading to get net.
  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: Measuring AC energy flow direction
    Voltage in a grid-tie household system is the same at all points, or close enough for practical purposes, as it is set by the Voltage source power supply; the grid. As has been repeatedly hammered into my deteriorating brain capacity the GTI is a current-based power source; its Voltage is fixed by the utility supply.

    As such:
    Loads are always negative power.
    GTI is always positive power (supplying loads and/or grid).
    Grid is either positive power (supplying) or negative power (consuming from GTI).
    Any one can be at zero power.
    If Loads > GTI output then Grid is positive power source.
    If Loads < GTI output then Grid is negative power source.
    If Loads = GTI output then Grid is at zero (exact power balance and highly unlikely).

    That is absolutely correct. What I had a problem with is the original wording of measuring current rather than power at three different points.
    At every point where you measure power, you must effectively measure (sense) both current and voltage, even if you are not allowed to read out the voltage.

    Now if you have CTs at each of those points and the CT wires along with one set of voltage wires is brought to a common location, you could locate all three power meters there and state that you are only measuring current at the other three points. But I feel that would be misleading.
    Rereading your post, I can see that it could be interpreted as measuring power at three different points even though there was a reference to current in between. :)
    SMA SB 3000, old BP panels.
  • igor1960
    igor1960 Solar Expert Posts: 85 ✭✭✭✭
    Re: Measuring AC energy flow direction
    inetdog wrote: »
    That is absolutely correct. What I had a problem with is the original wording of measuring current rather than power at three different points.
    At every point where you measure power, you must effectively measure (sense) both current and voltage, even if you are not allowed to read out the voltage.

    Now if you have CTs at each of those points and the CT wires along with one set of voltage wires is brought to a common location, you could locate all three power meters there and state that you are only measuring current at the other three points. But I feel that would be misleading.
    Rereading your post, I can see that it could be interpreted as measuring power at three different points even though there was a reference to current in between. :)

    I'm not sure if the solution to original question has been found (while reading the thread it's not that obvious), but just in case I think (and correct me if I'm wrong), but I think the simple solution is just that:

    Assuming we have pair of transducers like this: http://www.ebay.com/itm/Non-invasive-AC-current-sensor-SCT-019-200A-max-/150853751480 and
    assuming both of them are calibrated equally and assuming we have just 1 phase power supply:

    1. We install one around Main Power wire (L1) in the Main Panel (S1);
    2. We install another one around GTI dedicated circuit (S2);
    3. Now we connect S1 parallel to S2 (S1S2);
    4. Installed and connected signal Voltage of S1S2 would be approx. proportional to the sum of separate voltages in S1 and S2. However, if we rotate S2 180degrees (thus changing polarity of S2), then we will get as the result S1S2 signal voltage proportional to subtraction between S1 and S2.
    5. To find proper rotation of S2, we just need to see on sunny day with GTI working that when S2 is connected and S1 has some small extra load, we should have posive voltage on the signal wire of S1S2 and turning OFF S1 (all circuits on the main panel, except GTIs) should increase the voltage on S1S2: if voltage is negative, then S2 requires 180 degrees rotation and if turning OFF S1 (all circuits on the main panel, except GTIs) the voltage decreases, then S1 require 180degrees rotation.

    Looks extremely simple to me, as S1S2 signal voltage output with above setup would be mostly positive, when Generated Current would be more or equal to Load current (both phase and amplitude). And S1S2 signal voltage output would be mostly negative, when Generated Current would be less or equal to Load current (both phase and amplitude). 0 would correspond to Load exactly matching Generation.
    So, basically above setup takes in account both phase shifts and amplitudes between GTI generated current and Load current. Thus gives us signal somewhat proportional to those currents subtraction. We don't need exact subtraction current, as we will be just comparing to 0...
    Obviously, we need some kind of integrator/summator to accumulate signal voltages with at least AC frequency, but as GTI start on signal might be slow, our integrator might work with pretty low frequency (like 1hz or even less)...
  • bill von novak
    bill von novak Solar Expert Posts: 891 ✭✭✭✭
    Re: Measuring AC energy flow direction
    igor1960 wrote: »
    1. We install one around Main Power wire (L1) in the Main Panel (S1);
    2. We install another one around GTI dedicated circuit (S2);
    3. Now we connect S1 parallel to S2 (S1S2);
    Problem there; the current sense transformers will now fight and will not report an accurate current. However, if you use a burden resistor to convert current to voltage and then put them in series they will then either add or subtract, which I think is what you want. You still have an additional problem though:
    4. Installed and connected signal Voltage of S1S2 would be approx. proportional to the sum of separate voltages in S1 and S2. However, if we rotate S2 180degrees (thus changing polarity of S2), then we will get as the result S1S2 signal voltage proportional to subtraction between S1 and S2.
    5. To find proper rotation of S2, we just need to see on sunny day with GTI working that when S2 is connected and S1 has some small extra load, we should have posive voltage on the signal wire of S1S2 and turning OFF S1 (all circuits on the main panel, except GTIs) should increase the voltage on S1S2.

    If you do this, then zero volts will indeed indicate that generation is equal to supply.

    But what if you see a detection of 1 amp? Is that going in or out? Looking at just the combined output of the two sensors all you see is a sine wave with an amplitude of 1 amp. (Actually you see whatever voltage output the sensor gives you when it is sensing 1 amp.) You need more information than that, like a comparison of the phases between the GT sensor and the load sensor.
  • igor1960
    igor1960 Solar Expert Posts: 85 ✭✭✭✭
    Re: Measuring AC energy flow direction
    But what if you see a detection of 1 amp? Is that going in or out? Looking at just the combined output of the two sensors all you see is a sine wave with an amplitude of 1 amp. (Actually you see whatever voltage output the sensor gives you when it is sensing 1 amp.) You need more information than that, like a comparison of the phases between the GT sensor and the load sensor.

    Yes, I agree and I have realized that after posting. However, there might be simple solution.

    So, if we assume that S1 and S2 will be collecting values at the main Meter and on GTI circuit (let's forget for now about mentioned by you "current sense transformers will now fight and will not report an accurate current"(how significant that fight might be ?????) ):

    (1) S1 = Load + Generation, and is the same as NET current to/from the Meter at particular moment;
    (2) S2 = Generation, and is the same as GTI current at particular moment;
    (3) Load = S1 - Generation = S1 - S2, from (1 and 2) -- load current at particular moment;


    Then we might have an accumulator for ABS(Load) (AL) and accumulator for ABS(Generation) (AG)

    Assuming above, here is the sequence:

    1. We install one around Main Power wire (L1) in the Main Panel (S1);
    2. We install another one around GTI dedicated circuit (S2);
    3. Have 2 capacitors (or other accumulators) to integrate readings:
    -- AL: sum of absolute value subtractions between S1 and S2 (ABS(S1-S2) that would be double Load -- as we have absolute value);
    -- AG: sum of absolute S2 (that would be double Generation -- as we have absolute value);
    4. After some period (let's say 1 sec.) compare AL and AG:
    -- if AL > AG => then Load > Generation;
    -- if AL < AG => then Load < Generation;
    -- if AL == AG and obviously 0 => then Load == Generation;
    5. Zero both capacitors/accumulators AL and AG;
    6. Repeat from 4 to 5....

    Alternatively, having just 1 integer accumulator (A) and high frequency reading (let's say 1024hz):

    1. We install one around Main Power wire (L1) in the Main Panel (S1);
    2. We install another one around GTI dedicated circuit (S2);
    3. Repeat forever {
    Calculate NET = ABS(S1-S2) - ABS(S2) and if
    NET < 0 A++; if(A == 1) Fire Status changed
    NET > 0 A--; if(A == -1) Fire Status changed
    NET == 0 if (A > 0) { A--; } else if(A < 0) { A++; }
    if(ABS(A) == 1024) A=A/2;
    }
  • solar_dave
    solar_dave Solar Expert Posts: 2,397 ✭✭✭✭
    Re: Measuring AC energy flow direction

    Since you have 2 sensors and the generation is isolated it is pretty easy to just subtract the generation from the mains to get a net.
  • igor1960
    igor1960 Solar Expert Posts: 85 ✭✭✭✭
    Re: Measuring AC energy flow direction
    solar_dave wrote: »
    Since you have 2 sensors and the generation is isolated it is pretty easy to just subtract the generation from the mains to get a net.

    Not really: Main sensor already measures net, so subtractin Generation from Main will give you Load and not net...
  • bill von novak
    bill von novak Solar Expert Posts: 891 ✭✭✭✭
    Re: Measuring AC energy flow direction
    igor1960 wrote: »
    So, if we assume that S1 and S2 will be collecting values at the main Meter and on GTI circuit (let's forget for now about mentioned by you "current sense transformers will now fight and will not report an accurate current"(how significant that fight might be ?????) ):

    Unknown; they are not spec'd to operate like that. However that's somewhat immaterial since they can be connected in series to do what you want.
    3. Have 2 capacitors (or other accumulators) to integrate readings:
    -- AL: sum of absolute value subtractions between S1 and S2 (ABS(S1-S2) that would be double Load -- as we have absolute value);
    -- AG: sum of absolute S2 (that would be double Generation -- as we have absolute value);
    4. After some period (let's say 1 sec.) compare AL and AG:
    -- if AL > AG => then Load > Generation;
    -- if AL < AG => then Load < Generation;
    -- if AL == AG and obviously 0 => then Load == Generation;
    5. Zero both capacitors/accumulators AL and AG;
    6. Repeat from 4 to 5....

    If you're going to add a processor, just use a Cirrus CS5463. It is an integrated bidirectional power sensing IC. It gives you RMS (not peak) current and voltage, direction of current, power factor etc etc.
  • igor1960
    igor1960 Solar Expert Posts: 85 ✭✭✭✭
    Re: Measuring AC energy flow direction
    If you're going to add a processor, just use a Cirrus CS5463. It is an integrated bidirectional power sensing IC. It gives you RMS (not peak) current and voltage, direction of current, power factor etc etc.

    Not sure we need a processor.
    Here is circuit diagram I came up with:

    Attachment not found.


    2 Differential Amps, 2 Full-Wave Rectifiers, 1 AC Voltage converter

    Everything is working fine with the examples of max.+0.33V coming from transducers (S1).
    Output changes from positive to negative on 0.165V threshold in S2

    Even better this one (as I recall you proposed to put S1 and S2 in series, automatically getting S1-S2):
    Attachment not found.
  • solar_dave
    solar_dave Solar Expert Posts: 2,397 ✭✭✭✭
    Re: Measuring AC energy flow direction

    here is a typical solar/mains installation of a monitoring device.

    http://www.theenergydetective.com/solar

    They have a setting called adjusted load that does the proper math from the mains CT and the Solar CT. Personally I don't use this as I have my 3 loads separated from the generation.
  • igor1960
    igor1960 Solar Expert Posts: 85 ✭✭✭✭
    Re: Measuring AC energy flow direction

    If interested, here is my Final Solution:


    Attachment not found.


    S1 transducer at Main Panel (S2 + Load current voltage signal)
    S2 transducer at Generation (current in Generation circuit -- voltage signal: phase is around 180 degrees rotated to Load current voltage signal; around is because of Power Factor shift between Load and Generation)
    Circuits voltage at Out (Vout) would be equal to:
    -- Vn of integrator Amp if Generation is above the Load;
    -- Vp of integrator Amp if Generation is below the Load;
    Circuit imlements switch between Generation>Load to Generation<Load with some inertia, so it takes sometime for change of state (not instantaneous, but fast).
    Vp/Vn on other then integrator Amps could be any valid voltages...
  • igor1960
    igor1960 Solar Expert Posts: 85 ✭✭✭✭
    Re: Measuring AC energy flow direction

    Even better and simplier:

    Attachment not found.

    Circuits voltage at out (Vout) would be:
    -- negative, when house Load > GTI generation -- meaning: extra current received from utility;
    -- positive, when house Load < GTI generation -- meaning: there is surplus of energy and house system sends not used generated power to utility.

    Vout is limited by Vp/Vn of integrator Amps
    Circuit imlements switch between Load > GTI to Load < GTI with some inertia, so it takes sometime for change of state (not instantaneous, but fast).
    Vp/Vn on other then integrator Amps could be any valid voltages...
  • lazza
    lazza Solar Expert Posts: 336 ✭✭✭
    Re: Measuring AC energy flow direction

    HI

    This is all greek to me. Just to let you know a mate of mine has built a monitor using an arduino system based on the openenergymonitor.org website.
    But we've had two issues:

    1. Dumping the excess load is complicated, we were looking at several 100 to 200W small resistors and doing a semi-linear load control.
    2. He got married.

    So we stay in Spain without a real market for grid-tie systems. In fact the Government is so fossil-fuel-fascist that it has threatened to send inspectors into your house to find those harbouring solar panels. http://vozpopuli.com/economia-y-finanzas/34233-los-inspectores-podran-entrar-sin-orden-judicial-en-las-viviendas-que-produzcan-energia-solar. We can only dream of a net-metering paradise, they wont even let you use it for your own consumption without heavy fines/taxes.

    So we need to measure AC flow, which we've achieved, but then find away to linearly and safely dissipate the load. It's this last past that is really tricky

    Cheers
    Larry
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Measuring AC energy flow direction

    So, I guess this is the reason from the other thread why you don't want Wind turbines with dump loads? You need finer control of power flow to avoid back feeding electric meters?

    The article was not clear to me (bad translation link to English):

    http://translate.google.com/translate?hl=en&sl=es&tl=en&u=http%3A%2F%2Fvozpopuli.com%2Feconomia-y-finanzas%2F34233-los-inspectores-podran-entrar-sin-orden-judicial-en-las-viviendas-que-produzcan-energia-solar

    I could not tell if this was for Grid Tied solar, or as I believe, actually the "sun tax" where even if a person disconnects from the utility and installs solar panels+battery bank+AC inverters -- They still will be subject to inspections/fines/fees if the customer "leaves the grid"?

    In theory, it is already illegal in California to "disconnect from the grid" and use solar/other power sources without paying the utility for 20-40 years worth of loss revenue--There is currently a loophole that allows small residential and solar power systems to operate without fines/stranding fees.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • lazza
    lazza Solar Expert Posts: 336 ✭✭✭
    Re: Measuring AC energy flow direction

    No, the wind turbine systems are all off-grid. The customer would prefer without dump load... and so would I personally. In Andalusia putting a 1kw heater in a small room where the batteries are in summer is not a great method.

    I didnt know you had fossil fuel fascists there too! So much for the free world :cry:

    Yeah pretty much they are trying to do the same here.. but it's not quite all legislated yet